1. Field of the Invention
A xerographic photoreceptor primarily formed by the hydrogenated amorphous silicon material, wherein the xerographic photoreceptor is a photosensitive body manufactured by plasma enhanced low pressure chemical vapor deposition system. Such a xerographic photoreceptor has a higher resolution, and a longer lifetime.
2. Description of the Prior Art
The copy machine and laser printer have been developed and become more and more popular from 1938 due to a first work made by Chester F. Carlson and O. Kornei.
In 1969, R. C. Chittick, etc. disclose a method for manufacturing the hydrogenated amorphous silicon by the glow discharge. Then, the optoelectronic devices made of the hydrogenated amorphous silicon, such as solar cells, photo-transistors, optical detector and xerographic photoreceptor used in copy machine, laser printer and facsimile machine become the primary trend of such a material.
Besides, the photosensitive material used in the photoreceptor of the copy machine, laser printer, and facsimile machine is the most important elements in electrophotography technology. The characteristics of the material are related to the quality of copying. The materials, for example amorphous Se, CdS, and ZnO used in the prior art using the vacuum evaporation method, have a preferred photosensitivity. But they are easily to be worn away, and have a short lifetime. These are significant defects.
From the developing of the hydrogenated amorphous silicon in 1976, people pay attention to the excellent optoelectronic characteristics. Recently, the hydrogenated amorphous silicon applied to a photosensitive photoreceptor has been studied widely. Cannon has firstly developed commercial copy machines using the hydrogenated amorphous silicon photosensitive drum, which are NP-9030 (with semiconductor laser as a light source) and NP-7500 (with a halogen lamp as a light source). Comparing with the conventional photosensitive drums, for example, amorphous Se sad As.sub.2 Se.sub.3, it has the following advantages:
1. A preferred photoconductivity. PA1 2. A higher dark resistivity. PA1 3. A wider spectrum of photoconductivity. PA1 4. Higher light absorption coefficient. PA1 5. Manufactured by doping, the electrical property can be well controlled. PA1 6. Special homogeneous property so as to be easily deposited on most kinds of substrates. PA1 7. Stronger mechanical strength and elasticity. PA1 8. less poison in using PA1 (1) High surface charge accepting ability. PA1 (2) Preferred surface insulation. PA1 (3) ILow dark decay. PA1 (4) Quick light decay. PA1 (5) High photosensitivity. PA1 (6) Low residual potential. PA1 (7) Long lifetime. PA1 a. placing the aluminum substrate into a furnace, baking the aluminum substrate under a temperature of 90.about.95.degree. C. by a thermal oxidation method, thus the aluminum substrate is grown with the Al.sub.2 O.sub.3 oxidation layer (20.about.30 .ANG.); PA1 b. placing the aluminum substrate with the Al.sub.2 O.sub.3 oxidation layer into a gas deposition system, filling mixed gas (SiH.sub.4 /H.sub.2 =10%, 100 sccm; pH.sub.3 /H.sub.2 =3%, 10 sccm) into the system with the radio frequency power being set at 30 W. The temperature of the substrate is set at 150.degree. C., the deposition pressure is set as 0.75 Torr for growing a n type hydrogenated amorphous silicon blocking material (300.about.400 .ANG.) on the aluminum substrate with the Al.sub.2 O.sub.3 oxidation layer;. PA1 c. placing the n type hydrogenated amorphous silicon blocking layer on the aluminum substrate with the Al.sub.2 O.sub.3 oxidation layer into a gas deposition system, and filling into mixed gases (SiH.sub.4 /H.sub.2 =10%, 150 sccm) with a radio frequency power being set at 30 W. The temperature of the substrate is set at 150.degree. C., the deposition pressure is set at 2 Torr with a deposition time of 7 hours growing for growing an intrinsic hydrogenated amorphous silicon charge generation transport layer (15.about.16 .mu.m) on the n type hydrogenated amorphous silicon blocking layer on the aluminum substrate with the Al.sub.2 O.sub.3 oxidation layer; PA1 d. placing the intrinsic hydrogenated amorphous silicon charge generation transport layer on the aluminum substrate with the Al.sub.2 O.sub.3 oxidation layer into the gas deposition system, and then filling mixed gas (Si.sub.4 /H.sub.2 =30%, 100 sccm) with a radio frequency power being set at 40 W. The temperature of the substrate is set at 25.degree. C., the deposition pressure is set at 0.8 Torr with a deposition time of 20 minutes for growing a hydrogenated carbon surface protecting layer (300.about.400 .ANG.) on the aluminum substrate with the intrinsic hydrogenated amorphous silicon charge generation transport layer.
The prior art for the hydrogenated amorphous silicon xerographic photoreceptor can be referred to U.S. Patent Publication U.S. Pat. No. 5,252,418, in the patent, a method for preventing the vagueness of the hydrogenated amorphous silicon xerographic photoreceptor and improving the surface layer structure of the xerographic photoreceptor is disclosed so that it has a longer lifetime.
The prior art of the hydrogenated amorphous silicon xerographic photoreceptor can be referred to U.S. Patent Publication U.S. Pat. No. 4,943,503. In the patent, another structure of the hydrogenated amorphous silicon xerographic photoreceptor is disclosed, wherein a middle layer is deposited between the optical conductive layer and the surface layer. The middle layer is prepared by the amorphous silicon doped with nitrogen atoms or boron atoms.
A prior art for the hydrogenated amorphous silicon xerographic photoreceptor is disclosed in U.S. Patent Publication U.S. Pat. No. 4,913,995. In the patent, a functional separation method was served to prepare a xerographic photoreceptor. Wherein, the transport layer of the amorphous silicon alloy and the middle layer of the hydrogenated amorphous silicon photosensitive layer are charged by positive or negative corona, the xerographic photoreceptor has a high surface potential and lower residual potential.
The prior art for the hydrogenated amorphous silicon xerographic photoreceptor can be referred to U.S. Patent Publication U.S. Pat. No. 48,533,309. In the patent, a sandwich structure (blocking layer/photoconductive layer/surface layer) is disclosed, wherein a gradient concentration method was served to dope the amorphous silicon photoconductive layer.
A prior art for the hydrogenated amorphous silicon xerographic photoreceptor is disclosed in U.S. Patent Publication U.S. Pat. No. 4,804,608, wherein a simple xerographic photoreceptor structure is disclosed. Namely, the conductive substrate photoconductive layer; the photoconductive layer is formed by the amorphous silicon alloy (a-Si(1-m)X(m): Y). Wherein the X is C, N or O, Y is either H or F 0.ltoreq.m.ltoreq.1. The value m is reduced gradually from the surface of the photoconductive layer to the middle part, and is increased gradually from the middle part to the interface of the conductive substrate. Therefore, the xerographic photoreceptor has a preferred charging and photosensitive properties.
A prior art for the hydrogenated amorphous silicon xerographic photoreceptor is disclosed in U.S. Patent Publication U.S. Pat. No. 4,804,605. The patent discloses a xerographic photoreceptor structure with the superlattice. The structure is primarily formed by conductive substrate/blocking layer/photoconductive layer/surface layer. The photoconductive layer has the superlattice structure formed by alternatively stacked hydrogenated amorphous silicon and microcrystal hydrogenated silicon carbide. Both is formed as a potential well so that light is illuminated, a large amount of photo-generation carriers will be generated. And by transport effect, the photo-generation carriers will pass through the blocking layer.
A prior art for the hydrogenated amorphous silicon xerographic photoreceptor is disclosed in U.S. Patent Publication U.S. Pat. No. 4,732,833. In the patent, by mixing the amorphous silicon and superlattice microcrystal silicon, a photoconductive layer of the xerographic photoreceptor is prepared. The whole xerographic photoreceptor is aluminum/amorphous silicon carbide/amorphous silicon (superlattice microcrystal silicon and amorphous silicon).
A prior for the hydrogenated amorphous silicon xerographic photoreceptor is disclosed in U.S. Patent Publication U.S. Pat. No. 4,687,724. In the patent, another steady xerographic photoreceptor with high photosensitivity is disclosed. Namely, the material of the xerographic photoreceptor is amorphous silicon doped by nitrogen, hydrogen and fluorine, and the quality of copying is not be reduced with the operation increasing.
A prior art for the hydrogenated amorphous silicon xerographic photoreceptor is disclosed in U.S. Patent Publication U.S. Pat. No. 4,664,999. In the patent, a layer of amorphous carbon is deposited on the amorphous silicon.
A prior art for the hydrogenated amorphous silicon xerographic photoreceptor is disclosed in U.S. Patent Publication U.S. Pat. No. 4,533,564. In the patent, a method of the electrophotographic photoreceptor is disclosed. The photosensitive structure is approximately formed by a conductive substrate/blocking layer/hydrogenated amorphous silicon (P)/surface protecting layer.
A prior art for the hydrogenated amorphous silicon xerographic photoreceptor is disclosed in U.S. Patent Publication U.S. Pat. No. 4,532,196. In the patent, a plasma enhanced chemical vapor deposition technology was served serves to prepare an amorphous silicon xerographic photoreceptor. The xerographic photoreceptor is primarily formed by many kinds of doped amorphous silicon, the material compositions include SiH.sub.4,B.sub.2 H.sub.6, N.sub.2 and PH.sub.3. The xerographic photoreceptor has good photosensitivity, longer lifetime and without causing hurt of health for user.
A prior art for the hydrogenated amorphous silicon xerographic photoreceptor is disclosed in U.S. Patent Publication U.S. Pat. No. 4,513,073. In the patent, a photoconductive device formed by a photosersitive layer, one or more blocking layer, which the space charge layer is produced for increasing the acceptance voltage of the photoconductive device (initial surface potential).
Thus, the aforesaid prior arts disclose different methods for preparing the hydrogenated amorphous silicon xerographic photoreceptor. While in the present invention, a plasma enhanced chemical vapor deposition (PE-LPCVD) system was be served to deposit to a multiple layer inorganic xerographic photoreceptor which is photosensitive in visible light and the lifetime of the xerographic photoreceptor is prolonged.
Isamu Shimizu, etc. describe the technology of preparing the hydrogenated amorphous silicon xerographic photoreceptor is difficult. But this difficult is resolved until after the glow discharge method is applied. However, according to L. B. Schein in Electrophotography and Development Physics, 2nd Edition, McGraw-Hill, New York, 1992, discloses the current hydrogenated amorphous silicon xerographic photoreceptor having the thickness of several tens of micro-meter (&gt;20 .mu.m). Thus, the initial surface potential must be as high as 400V for developing. Therefore, the cost and manufacturing technology is the primarily consideration.
Besides, according to J. Mort and F. Janced in Plasma Deposited Thin Films, Chap. 7, pp.187-204, CRC Press, Inc., Florida, 1986, describes that since the thickness of xerographic photoreceptor the is larger than 20 .mu.m, thus the accepting ability of the surface charge is affected and limited by the substrate and the surface carrier effect carrier. In the condition that carrier injection to the substrate, a blocking layer can be grown between the substrate and the xerographic photoreceptor. The material can be selected as Si.sub.3 N.sub.4, SiO.sub.2, P type hydrogenated amorphous silicon (200 ppm Boron, .about.0.3 .mu.m). Once the thickness of the xerographic photoreceptor is larger than 20 .mu.m. The conductivity of the hydrogenated amorphous silicon xerographic photoreceptor becomes more and more important and is limited. Moreover, no matter what kinds of materials used in the xerographic photoreceptor, the accepting ability of the surface charge thereof must be in the range of 20.about.30V/.mu.m for conforming the requirement of a xerographic photoreceptor.
A preferred xerographic photoreceptor must meet the following characteristics:
Therefore for a hydrogenated amorphous silicon xerographic photoreceptor, other then a structural design of function separation, the preparing technology and manufacturing cost must be further considered.